Check out "anotherairgunblog" site, he shows the re-seal, they're pretty simple
I have industry brand qs35. These look about the same except mine is a under lever fixed Barrel. I just shot it over the speed o meter. using flat heads a even 350 fps, but using cr pointed is at 409 to 424 fps. I tried to diesel it and came up with 398 and a smoke cloud.I drop my head and say I like the ugly thing. it's heavy, looks more like a club than a pistol. if it gives up, there is enough wood to get a fire started (shtf), could use it for a hammer.
I had a .22 and .177. I think I gave them away. Fun little guns. After practice and zeroing and a little Kentucky windage I could hit a sheet of copy paper at 25 yards consistently off a rest.I wonder if the barrel scope mounts for a 1377/22 would work on the barrel of the Pioneer pistol with a pistol scope.